1. Field of the Invention
The present invention relates to a position controller for an optical element which can be moved to correct image shake and removed to a position outside an anti-shake driving range of the optical element.
2. Description of the Related Art
Conventional anti-shake drive mechanisms using a voice coil motor (VCM) are provided with a constrained frame, the position of which in directions orthogonal to an optical axis is constrained, an anti-shake movable frame (image-stabilizing lens) which is supported by the constrained frame to be movable in direction orthogonal to the optical axis, and an anti-shake drive actuator (anti-shake coils); and the anti-shake movable frame is driven and controlled in a plane orthogonal to the optical axis relative to the constrained frame by controlling the passage of electric current through the anti-shake drive actuator (anti-shake coils). In such anti-shake drive mechanisms, no operation for holding the anti-shake movable frame at a specific position when no current is passed through the anti-shake drive actuator (anti-shake coils) is performed, and accordingly, to prevent the anti-shake movable frame from rattling, it is required to lock the anti-shake movable frame with respect to the constrained frame using a separate member from the anti-shake movable frame.
For instance, in Japanese Unexamined Patent Publication No. 2010-271607, the anti-shake drive mechanism is provided with a movement limit member (lock shaft) which is movable by rotating in a plane orthogonal to an optical axis between a movement limit position, in which an anti-shake movable frame (image-stabilizing lens) is prevented from moving, and a movement limit release position, in which the anti-shake movable frame (image-stabilizing lens) is allowed to move, and the anti-shake movable frame (image-stabilizing lens) is locked by positioning the movement limit member in the movement limit position when no current is passed through an anti-shake drive actuator (anti-shake coils). In addition, in Japanese Unexamined Patent Publication No. 2010-128389, the anti-shake drive mechanism is provided with a return magnet which is a separate member from the anti-shake magnets of the anti-shake drive actuator, and this return magnet is used to center an anti-shake movable frame (image-stabilizing lens) when no current is passed through an anti-shake drive actuator (anti-shake coils).
On the other hand, a technique for removing (radially retracting) an image-stabilizing lens to a position off an optical axis of a lens barrel when an optical device that incorporates the anti-shake drive mechanism moves from an operating state (ready-to-photograph state) to a lens barrel accommodated state (fully retracted state/non-operating state) in which no pictures are taken, has been proposed for the purpose of making the lens barrel compact in size (slimming the lens barrel) with respect to the optical axis direction. For instance, in Japanese Unexamined Patent Publication No. 2007-206210, an image-stabilizing lens is pivotally supported by an anti-shake movable frame which moves in a plane orthogonal to an optical axis by an anti-shake drive actuator (anti-shake coils), and after the commencement of the movement of the anti-shake movable frame from a ready-to-photograph position to the lens barrel accommodated position that is caused by a main actuator (zoom motor), firstly the anti-shake movable frame is centered by the anti-shake drive actuator and fixed by a stopper member, subsequently the passage of current through the anti-shake drive actuator is shut off, and lastly the image-stabilizing lens is removed to a position off the optical axis by a removal drive member (cam bar).
However, in the structure disclosed in the aforementioned Japanese Unexamined Patent Publication No. 2007-206210, since the retractive movement of the anti-shake movable frame that is caused by the main actuator commences with electric current remaining passed through the anti-shake drive actuator, excessive current is passed through the anti-shake coils as a result of the anti-shake drive actuator continuing to drive the anti-shake movable frame to move the anti-shake movable frame to the initial position thereof during the retractive movement of the anti-shake movable frame, which may cause damage to the anti-shake drive actuator and waste electrical power.